Adjustment of magnetic starters and contactors. Operation and repair of magnetic starters. Adjustment of electromagnetic starters and contactors

22.09.2023

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Magnetic starters, as the name suggests, were conceived as a switching device for starting electric motors. Therefore, the number of power poles in these devices is almost always equal to three - according to the number of phases of the network. Starters are often equipped with thermal overload relays and a housing with start and stop buttons.

But the starter turned out to be a very convenient and functional thing. A wide range of rated currents, small dimensions and the possibility of autonomous installation outside any switchgear or panel have led to the fact that magnetic starters began to be widely used in everyday life for connecting various powerful electrical receivers, for example, heating boilers, to the network.

Like any other electrical device, a magnetic starter also periodically needs repair and maintenance.

How does a magnetic starter work?

In general, this is at least a coil of thin wire in varnish insulation, housed in the same plastic housing with contacts. Contacts, as usual, are divided into movable, mechanically connected to the spring-loaded core of the coil, and fixed, permanently located in the upper part of the housing.

At the same time, for starters designed for a current of 20 amperes or more, one can clearly distinguish between three pairs of power pairs of contacts, and pairs of contacts of auxiliary control circuits, designed for low currents. The number of low-current contacts is practically unlimited, especially since for many starters it is possible to purchase additional contact attachments that allow you to assemble very complex circuits on starters.

This design provides the starter with a not particularly high degree of protection from external influences - at the IP00-IP30 level. If it is necessary to achieve a greater degree of protection, you will have to use starters in an additional protective casing, often equipped with their own buttons for starting, stopping and returning the thermal relay, if any.

Rice. 1. PML magnetic starter device:

1 - base made of heat-resistant plastic, 2 - fixed part of the magnetic circuit, 3 - moving part of the magnetic circuit, 4 - electromagnetic control coil, 5 - contact clamps, 6 - metal platform (for starters rated over 25 A) 7 - traverse with moving contacts, 8 - mounting screw, 9 - return spring, 10 - aluminum rings, 11 - fixed contact, 12 - clip with a notch for fixing the conductors.

The maintenance program for magnetic starters is simple and includes the following items:

1. External inspection for damage and chips of the housing, as well as removing contaminants (not only from the surface of the housing, but also from the surface of the electromagnet core). Chips and damage to the housing occur not only due to impacts and falls, but also due to prolonged exposure to vibrations caused by the operation of a worn-out AC network and faulty installation of the starter, as well as its own defects.

If damage to the housing has led to the fact that the starter cannot be securely fastened, or its contacts cannot open/close freely, then there is simply no other option than replacing the housing or starter.

Special attention should be paid to checking the presence of all parts and components of the starter. For example, a movable contact plate along with its preload spring can easily be “lost” - a new one will be required.

V. A. Smirnov, K. V. Panov

EDUCATIONAL MANUAL

for PERFORMING laboratory WORK

WHEN STUDYING A DISCIPLINE

"Production and REPAIR OF ROLLING STOCK"

Part 2

UDC629.4.083: 629.488

Educational and methodological manual for performing laboratory work when studying the discipline “Production and repair of rolling stock.” Part 2 / V. A. Smirnov, K. V. Panov. Omsk State University of Communications. Omsk, 2016. 31 p.

Developed in accordance with the discipline program “Production and repair of rolling stock”. Contains basic information about technological processes for repairing components and assemblies of electric rolling stock. The educational manual consists of two parts. The second part includes four laboratory works devoted to the study of technological processes for revising electrical devices.

Intended for fourth-year students of the specialty “Railway Rolling Stock”, specialization “Electric Transport of Railways” and “High-Speed Ground Transport”, full-time and part-time courses. The educational and methodological manual can be used to train students in blue-collar professions and during training courses for railway transport workers.

Bibliography: 4 titles. Rice. 4.

Reviewers: Dr. Tech. Sciences, Professor V.A. Kruczek;

Ph.D. tech. Sciences, Associate Professor O. V. Balagin.

___________________________

Railways, 2016

Introduction. 5

Laboratory work 5. Inspection of individual contactors. 6

5.1. General information. 6

5.2 Work order.. 10

5.3 Used measuring tools and devices. eleven

5.5. Test questions.. 11

Laboratory work 6. Revision of a group switch. 12

6.1 General information. 12

6.2 Work order.. 15

6.3 Used measuring instruments and devices. 16

6.5. Test questions.. 17

Laboratory work 7. Inspection of a high-speed switch. 17

7.1 General information. 17

7.2. Work order... 22

7.3. Used measuring instruments and devices. 23

7.5. Test questions.. 24

Laboratory work 8. Inspection of the pantograph. 24

8.1 General information. 24

8.2. Work order... 27

8.3. Used measuring instruments and devices. 28

8.5. Test questions.. 28

Bibliographic list. thirty

INTRODUCTION

During the operation of electric rolling stock (EPS), wear of the rubbing surfaces of parts, aging of insulation, the appearance of fatigue cracks, and disruption of the adjustment of components occur.

The entire process of repairing a part, assembly, piece of equipment or an electric locomotive as a whole is conventionally divided into four independent technological processes: cleaning, defect detection, repair and testing (acceptance), performed in specialized positions. These works form the basis of the technological process of repairing any electric locomotive bridle.

Laboratory work is intended for students to more deeply study repair technological processes, as well as acquire practical skills in identifying defects, adjusting and testing individual components and assemblies of EPS.

The second part is devoted to the study of technological processes for revising electrical devices: individual contactors, group switches, high-speed switches and pantographs.

Students prepare for laboratory work in advance, independently, using the literary sources indicated in the guidelines. The student is allowed to perform the next work only after an interview with the teacher, as well as if there is a report on the previous work.

During laboratory work, the student uses literary sources, repair manuals and instructions from JSC Russian Railways, posters, measuring instruments, tolerance control tools and devices recommended by guidelines. Work is carried out by teams of no more than four people.

Each student completes reports on all work individually in a special notebook. The preparation of reports must comply with the requirements of the guidelines, as well as the approved standards of the enterprise (university).

Particular attention should be paid to compliance with safety rules, instructions on which are given by the teacher before the start of each laboratory work.

Laboratory work No. 5

REVISION OF INDIVIDUAL CONTACTORS

Purpose of the work: to gain practical skills in checking parameters, assessing performance and identifying defects of individual electropneumatic and electromagnetic contactors. Familiarize yourself with the technology for inspecting individual contactors and methods for eliminating defects.

General information

Inspection, revision and repair of individual contactors are carried out in accordance with the requirements of the Electric Locomotive Repair Manuals.

Individual contactors are subject to inspection and revision at TP-1 and TP-2. At the same time, the arc-extinguishing chambers are removed from the contactors and sent to the workshop for more thorough cleaning of carbon deposits and blowing with compressed air. The contactors themselves are inspected and repaired directly on the electric locomotive. Repairs involving disassembly of contactors are carried out using TR-3 with removal from the EPS.

When performing laboratory work, operations are provided in the scope provided for by the technological process of inspecting individual contactors during routine repairs of TR-1.

On an electric locomotive, they check by ear the clear operation of all devices when switched on from the control cabin, and control the operation of electrical circuits. Pay attention to the proper operation of the pneumatic drive. It is advisable to carry out such a check together: one mechanic controls the devices from the remote control in the driver’s cabin, and the other, being in the high-voltage chamber, carefully monitors the switching on and off of the devices and makes sure that there are no air leaks from the pneumatic system.

Usually, based on the first check, it is possible to draw a conclusion about the condition of the device and even establish the cause of the damage. For example, an electro-pneumatic contactor turns on clearly, but turns off slowly. This may be due to a jammed moving system, damage to the trip spring, or loosening of its fastening.

After checking the functioning, the arc chutes are removed, the dimensions and wear of the parts are checked for compliance with existing tolerance standards, cleaned of dust and carbon deposits, and blown with compressed air at a pressure of 300-350 kPa (3-3.5 kgf/cm2).

Using feeler gauges, the gaps in the hinges are measured, as well as the diameters of the rollers, axles, bushings and holes. Rollers and axles whose dimensions are equal to the maximum values are replaced. The normal operation of the devices can be disrupted not only as a result of large wear in the hinges, but also due to the formation of scoring in them or lack of lubrication. There are frequent cases of welding of hinges as a result of the flow of short circuit currents, breakage or loosening of copper shunts. To identify possible jams, the operation of the moving systems of the devices is checked by lightly moving them by hand.

Be sure to make sure that all free rotation axes are pinned or secured from falling out in some other way. When changing components and parts, it should be remembered that bolted connections must have spring washers or, in accordance with the drawings, must be secured in another way to prevent the bolts and nuts from being unscrewed.

The condition and fastening of power and low-voltage wires is checked. Wire tips with a break of more than 20% of the wires, with loose soldering, cracks or a contact surface reduced by more than 1/3 must be replaced and re-soldered.

The condition of the insulation of wires, coils of electromagnetic valves, including electromagnets, and the surface of insulating posts is checked. They may have both electrical and mechanical damage. Damaged glaze of porcelain insulators, damage to the crimping surface of contactor stands are usually washed from soot and dirt with napkins soaked in gasoline, cleaned with glass cloth and coated with NTs-925 varnish or GF-92HK enamel.

An electric arc, when there is a disruption in the arc extinguishing process or a short circuit, often burns and chars the insulation of arc extinguishing coils and racks to a layer of mica and even to metal. If only the outer layer of insulation is damaged, the burnt area is cleaned with a glass cloth, then thoroughly washed with gasoline and covered with enamel.

An important condition for maintaining the functionality of electrical devices is the regular addition of lubricant to the friction unit. If necessary, lubricant is added to the hinges of the moving parts of devices where friction of steel on steel or on brass occurs.

External inspection and measurements of wear, tear and contact pressure values check the technical condition of the moving and fixed contacts. When starting to clean contacts, especially power ones, they evaluate the color, size of the melting and the nature of the spread of frozen copper splashes over the surface of the contacts. The main reason for the deterioration of the contacts is a decrease in their pressure. It occurs not only from incorrect adjustment of the device, jamming of its moving parts, but also in the event of damage or misadjustment of the lapping, turning on or off spring. The spring may also lose its elastic properties due to excessive heating when the fastening is loosened or the copper shunt bridging it is broken, the electric arc is transferred, or the contacts of the device become unacceptablely heated. The consequences of reducing contact pressure are significantly aggravated by the dynamic effects of the body, leading to “rattling” of the contacts of the switched on device.

Another reason for excessive heating may be improper mating of the contact surfaces, which leads to burnout of the metal at the point of contact and the formation of a spot with a rough surface. Subsequently, these burns cause darkening of the entire contact and its melting. Repair manuals state that the length of the contact line must be at least 80% of the contact width. To test the touch, carbon paper and thin (tissue) paper are used. Retracting the moving contact with your hand, place carbon paper and blank paper between the contacts, and use your son-in-law to lower the moving contact. The touch line is clearly imprinted when the contacts collide. The lateral displacement of the contacts should not exceed 1 mm.

The contact pressure is checked with a spring dynamometer. Considering that the springs pressing the contacts have significant rigidity, the pressure is controlled directly at the moment of separation of one contact from the other. To do this, a thin strip of paper is clamped between the contacts (Fig. 5.1, a). Then, hooking the dynamometer to the movable contact, pull it strictly along the shutdown line, while simultaneously applying force to the strip of paper. To eliminate errors in measuring contact pressure, the attachment point of the dynamometer must be chosen so that the line of application of force to the dynamometer passes through the point of contact of the contacts.

Rice. 5.1. Checking the controlled parameters of the contactor

Important factors that determine the stable operation of movable contact connections are solution (rupture or opening), rubbing and failure of contacts. The solution is the shortest distance A between the contacts of a completely switched off contactor (Fig. 5.1, b). For most devices, it is convenient to measure the contact opening with a caliper, but it is more advisable to use pass-through and non-pass-through templates.

The rubbing of the contacts is checked when the contactor is turned on manually by directly observing the rolling of the contacts. In this case, the moving contact lever must have some free play after the contacts come into contact. It is also necessary to keep in mind that good lapping is ensured by the geometric dimensions of the moving contact parts, the engaging and lapping springs, and the shape of the contacts. For contactors it also depends on the failure of the moving contact.

By failure we mean the distance that the moving contact could travel if the fixed contact was removed from a fully switched on device. However, in reality it is not possible to measure this distance. Therefore, failure is determined indirectly by the gap between the contact holder and the lever (Fig. 5.1, c).

Work order

1. Study the procedure and content of inspection and audit of individual electromagnetic and electro-pneumatic contactors of an electric locomotive, become familiar with possible malfunctions and methods for eliminating them

2. Inspect and audit the individual contactor as directed by the teacher. At the same time, by inspection, evaluate the technical condition of contacts, arc extinguishing devices, brackets, racks, pneumatic and electromagnetic drives of individual contactors.

3. When inspecting contactors, check the condition of the flexible shunts of the arc extinguishing coils, their fastening, measure the thickness, gap, pressing, failure, lateral displacement of the contacts and the line of their contact. Check the operation of contactors at the minimum permissible values of compressed air pressure and voltage of the electrical control circuit of the electric locomotive, measure the contact pressure values. Enter the results of inspection and measurements in the table. 5.1.

Based on a comparison of the actual values of the monitored parameters with the acceptable ones, make a conclusion about the (un) suitability of individual contactors for operation, as well as the need to replace individual components and parts or carry out repair work to eliminate detected defects.

Table 5.1

Contactor inspection and measurement results

The maintenance program for magnetic starters is simple and includes the following items:

2. Revision of the mechanical part. The operating spring, which ensures the contacts are broken, is tested. It should be quite rigid, the turns should not get too close. The movement of the starter armature relative to the housing is checked: it is necessary that there are no jams or difficulties during movement.

Checking the progress is carried out by closing the contacts “by hand”. If there are mechanical jams, you can resort to lubrication or grinding of the rubbing parts.

3. Cleaning contacts– a measure that is best avoided when carrying out maintenance of serviceable magnetic starters.

The highly conductive layer of movable and stationary contacts is relatively thin, therefore, if you rub a file on it during each maintenance, the starter will very soon fail. A file will only be needed if there are obvious traces of carbon deposits or melting on the contacts. Sandpaper for cleaning contacts is strictly excluded.

When closing, all contacts of the starter must fit tightly against each other over the entire surface, without displacements or tilts, the presence of which indicates the need to adjust the mechanical part.

4. If the starter contains metal parts in the housing, or is located in a metal casing, then it is necessary to ensure that there is no circuit between these parts to be grounded and the power contacts. For all starters in general, it is necessary to check the absence of short circuits between the individual power poles. At the household level, for these purposes it is enough to use a conventional multimeter. A megohmmeter is used in production, and the insulation resistance is standardized - at least 0.5 Mohm.

5. The starter coil is thoroughly inspected. Cracks in the frame, damage, carbon deposits and melting of insulation are all sure signs of significant problems. It is better to replace a coil with such symptoms.

Of course, usually it is possible to determine an interturn short circuit in a coil only during operation by indirect signs, such as an increased hum when the starter is operating. However, if you systematically check the active resistance of the coil wire, you can notice a significant and sharp decrease. This sign speaks quite eloquently about the malfunction of the coil, which theoretically can be rewound, but in practice is easier to replace.

6. However, an increased hum during starter operation can be caused by some other reasons besides defects in the coil itself. For example, a misalignment may occur during its installation, the voltage level in the network may be insufficient, or the return spring may be selected too strong.

All these factors lead to the fact that the armature does not fit tightly enough to the core when closing. The consequence will be a higher coil current due to its lower inductive reactance (hence the hum), as well as burning of the power contacts.

You can check the tightness of the surfaces of the magnetic circuits of the core and armature using an ordinary thin blank piece of paper placed between these parts. At least 70 percent of the surface must be in contact - then the contact will be reliable.

7. If there is a thermal overload relay, its setting should be checked. At industrial enterprises this is done using special test benches. Unfortunately, at the household level it is almost impossible to load and test the relay. To do this, you can take the relay to a special laboratory, or, as a last resort, test it using a known load of a higher rating.

Magnetic starter repair is carried out based on the results of maintenance and usually comes down to the replacement of parts and assemblies that cannot be restored or adjusted. Such spare parts can be: a coil, individual contacts and even the contact group as a whole, housing parts, springs, screws and clamping plates.

On the surfaces of which there are traces of burning and soot, clean with a cotton cloth soaked in white spirit or aviation gasoline.

Splashes and “kings” of metal on the surface of the contacts are cleaned with a needle file. After cleaning, use a 0.05 mm thick probe to check the tightness of the contact surfaces. With closed contacts, the probe should not pass between the contacts more than 25% of the contact surface.

If the contact spring is broken or weakened, replace it with a new one or one suitable from a rejected starter.

If the threads in the holes for the screws for fastening the current-carrying wires are worn out or broken, the holes with damaged threads are drilled out and the threads of the next size are cut with a tap.

Repair of magnetic circuits of magnetic starters

The magnetic cores of magnetic starters consist of an armature and a core on which a short-circuited coil is mounted.

Contaminated contact surfaces between the core and the armature are cleaned with a cleaning material soaked in gasoline. If there are traces of corrosion on the contact surface, the surface is cleaned with sandpaper. After cleaning, use a 0.05 mm thick probe to check the contact area between the core and the armature by pressing the armature against the core with your hand. The contact surface must be at least 70% of the core cross-section.

If the air gap between the middle cores of the armature and the magnetic core is less than 0.2 mm, the armature or starter core is clamped in a vice and the middle core is filed with a finely cut file. Then the armature is applied to the core and the gap is checked with feeler gauges. The gap size should be in the range of 0.2 - 0.25 mm. When filing the core, make sure that the surfaces of the middle cores of the armature and core are parallel when closing the magnetic system.

When work hardening, the contact surfaces of the core and the armature are ground on a grinding machine until traces of work hardening are removed. After grinding, use feeler gauges to check the gap between the middle cores, as well as the area of contact between the outer cores of the armature and the core. The gap between the middle cores must be within the above limits, and the contact area of the outer cores must be at least 70% of the cross-section of the cores.

The damaged short-circuited coil in the starters is replaced with a new one. The damaged short-circuited coil of the starters is filed off on one side and removed.

The place where the coil is installed is cleaned with a needle file. The new short-circuited turn is made of brass. Replacing the material and manufacturing a short-circuited coil with dimensional deviations is prohibited, as this leads to an increase in the buzz of the switched on starter or to unacceptable heating of the coil.

The manufactured short-circuited turn of the starters is pressed into the grooves of the core or put on the core and the plates securing it are bent.

If the surface of the magnetic circuit has damaged coloring, clean it with a cleaning material soaked in gasoline or white spirit and dry it. After drying, the core and the anchor are lowered into a bath of enamel so that the contact surfaces are not covered with varnish, and the width of the unpainted belt around the edges of the contact surface should be no more than 3 mm. You can also paint the core and armature of the magnetic circuit with a brush.

The painted surfaces are air dried for 2 - 3 hours.

Repair of output terminals of magnetic starters

Burnt or oxidized contact surfaces of the terminal clamps are cleaned with a needle file or sandpaper, wiped with a cleaning material soaked in gasoline, and tinned with POS-30 solder.

If the threads in the holes for the screws for fastening the current-carrying wires are worn out or broken, the holes are welded with copper or brass using a gas torch. The welding area is cleaned with a file, punched and a hole is drilled for cutting a new thread. A thread is cut in the drilled hole to the size of the damaged thread.

A magnetic starter is essentially a switching device whose task is to connect and disconnect the load from the network.

Such devices are widely used mainly in industry and control of electric motors, but a wide range of rated currents and small dimensions of the device also make it possible to effectively find applications in everyday life.
In magnetic starters, moving or stationary elements and arcing contacts most often fail.

What is a magnetic starter?
First of all, to begin with, this is a coil, usually made of thin wire, wound on a textolite body with a metal core inside, placed in a kind of plastic case with contacts. The contacts in the device are divided into movable, mechanically connected to a spring-loaded coil core, and fixed, permanently placed in the upper part of the housing.

When the starter operates intensively, metal deposits, as well as soot and oxides, form on the contact plates of the device. All this is cleaned using a fine-cut file or needle file. After a good cleaning, the contacts are washed with a cloth that can be soaked in white spirit or can also be used in aviation gasoline.
But still, it is better to avoid this procedure in working starters, since the current-conducting layer on the contacts of the device is quite thin and each “preventative cleaning” will reduce it.

The contact planes of the armature and the core are cleaned with a soft rag soaked in alcohol. After cleaning with a 0.05 mm wide probe or a narrow piece of paper, you need to check the contact area between the core and the armature by pressing the armature against the core with your hand.
The contact plane must be more than 70% of the core cross-section. If this gap is less than 0.2 mm, the armature or starter core must be clamped in a vice and the central core must be cut off using a file. The value of this interval must remain within 0.2 - 0.25 mm.

Often during operation of the device a hum is heard, there may be several reasons. First of all, you need to inspect the cracks on the coil frame; perhaps there is a misalignment of the coil itself, or the return spring is too powerful.
All this can lead to the fact that the armature does not adhere closely enough to the core when closing. The consequence will be a higher coil current due to its lowest inductive resistance (hence the hum), as well as burning of the power contacts.

Failure of the coil itself is also likely; they come in both frame and frameless.
At defective coil insulation or breakage of the winding electrical wire in the upper layers of the winding, remove the external insulation of the winding and the warped turns to the point of the defect or break, add solder, insulate the soldering area of the new winding electrical wire and wind the required number of turns.
Although sometimes when the coil defects are significant, interturn short circuits, winding insulation burns, it is much better to replace the coil with a new one.

Sometimes when contacts are closed it happens different timing of plate closure, you can try to fix it by tightening the clamp holding the main contacts on the shaft.

If the surface magnetic plates It has damage and defects, it is cleaned with a soft cloth soaked in gasoline or white spirit and dried. And after drying, the core and the anchor are lowered into a bath of enamel so that the contact surfaces are not covered with varnish, and the width of the unpainted belt around the edges of the contact surface should be no more than 3 mm. You can also varnish the armature and the core of the magnetic circuit using a brush. After painting, the magnetic circuit is dried in the open air for 3 hours until completely dry.

Having identified all the malfunctions of the magnetic starter, you can simply replace some parts with new ones; such elements can be coils, springs, clamping plates, as well as contacts and entire contact groups.

Adjustment of magnetic starters and contactors. Operation and repair of magnetic starters. Adjustment of electromagnetic starters and contactors

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